ABSTRACT
OBJECTIVE: This study sought to assess the influence of cervical preflaring and reuse after resterilization, on fracture strength and plastic deformation and/or surface cracking in reciprocating nickel-titanium [NiTi] endodontic instruments after root canal instrumentation of extracted human teeth. MATERIALS AND METHODS: Forty engine-driven reciprocating NiTi instruments (20 Reciproc® [RC], VDW; 20 WaveOne® [WO], Dentsply) were used in root canal instrumentation of extracted human molars. A total of 485 human upper molars with similar anatomical features were selected and randomly distributed across four groups according to the instrumentation procedures performed (G1 and G3: RC; G2 and G4: WO). Reciprocating instruments were used as per manufacturer instructions. In groups G3 and G4, cervical preflaring was performed prior to instrumentation. After each use of each instrument, sterilization was repeated and scanning electron microscope (SEM) images were obtained to check for plastic deformations and/or cracks on instrument surfaces. Each instrument was used repeatedly until fracture occurred. RESULTS: Regardless of flaring, RC files exhibited greater fracture strength than WO instruments (P <0.01) with and without preflaring. Cervical preflaring significantly reduced the risk of instrument fracture (P <0.01). No plastic deformations were observed before fracturing. However, cracks were found on WO instruments shortly after their first use. RC and WO instruments resisted fracturing after autoclave sterilization. CONCLUSIONS: Cervical preflaring allowed a significant increase in the number of times RC and WO files could be reused safely.
ABSTRACT
O objetivo deste estudo foi comparar histologicamente o processo de cicatrizaçãode feridas cutâneas em dorso de 15 ratos machos adultos, após duas aplicações tópicas diárias deóleo-resina de copaíba, digluconato de clorexidina a 0,12% e soro fisiológico em três períodospredeterminados de 1, 7 e 15 dias. Os resultados histológicos quantitativos demonstraram umaredução estatisticamente significante no grau de inflamação nos três grupos (p < 0,05), embora ogrupo soro fisiológico tenha apresentado uma inflamação mais severa no dia 1 (p < 0,05). A análisehistológica qualitativa demonstrou que, nos períodos inicial e final, havia um padrão semelhantede cicatrização entre os tratamentos. Entretanto, no período intermediário de 7 dias, as feridascutâneas estavam completamente epitelizadas apenas nos grupos clorexidina e copaíba, apesar deeste apresentar um processo de reparo do tecido conjuntivo mais lento. As feridas cutâneas tratadascom solução aquosa de digluconato de clorexidina a 0,12% apresentaram uma cicatrização maisrápida quando comparadas àquelas tratadas com soro fisiológico e óleo-resina de copaíba.
The aim of this study was to compare by histological analysis the effects of twoexperimental solutions on wound healing. Standartized circular wounds were performed in theback of 15 adults rats. The wounds were rinsed twice a day for 15 days, using the followingexperimental solutions: 0.12% chlorhexidine digluconate (Group 1) and copaiba oil-resin (Group 2).In Group 3 (control) saline solution was used. All groups showed a statistically significant reductionin inflammation (p < 0.05), although the group 3 had presented severe inflammation at day 1(p < 0.05). At the days 1 and 15 the wound healing was similar among groups. However, at7 days the wounds were epithelized in the groups 1 and 2, although the granulation tissue couldbe observed in group 2. Thus, the use of 0.12% chlorhexidine digluconate rinsing solution canenhance the wound healing in comparison to copaiba oil-resin and saline solution.
